Blast-fan.



BL'ST'PAN.

APPLIOATIOH FILED MAR. 11, 1908.

4 SHEBTS-SHEET 1.

Patented Dec.

D. E'. LEPLY.

BLAST FAN.

APPLICATION ruim MAR. 11, 190B.

1908. SHEET 2.

Fatented Dec. l,

4 SHEETS-- vi [misses D.. F. LEPLEEL BLAST ma'.

BPFLIOATION 'ILED MAB. 11, 1908. L

4 SHEETS-SHEET 3.

neaavonononL-onau 0 llenan aoaunnageon @Mmmm awww/wm. l Y mom@ D. F, LEPLEY, BLAS-1' 1am APPLIGATION FILED MAE. 11, i908.

Fatente Dec. IES.

llld'i'lED STATES PATENT FECE.

DANIEL r. LErLEy, o iLcQNNELLsviLLE, rENNsi'LvaNiA BLAST-FAN.

Specification of Letters Patent.

Patented Dec. 1, 1908.

Application lile March. 11, 1908. Serial No. 420,482.

particularly ,for use where a.' large volume of ain under suflicient pressure to drive the same for long distances is desired.

Experience has demonstrated that for best.

results the blast fan should have the center of the fan wheeler rotor of open construction with the blades -designed to direct air toward the periphery 'of the fan from whence the air is conducted .to the point of'htiliza# tion.

It is the object of the'present invention to so construct blast fans of the open center type as to avoid certain objectionable features which have been found to be present 'in blast fans as heretofore constructed,

By arranging the blades tangentiallyto a circle less than the diameter of the central' orifice or intake of the fan, the air entering through such intake isl scooped up and directed toward the periphery of the fan and there thrown .off into a suitablechamber from whence the air is conducted away.-

T he tangential blades are of course -further apart-at their outerends than at their inner ends and air taken into the rotor at the in? Atake ends of the blades is by the rotative motion of the fan body caused to be packed,

or compressed against the active faces of the blades. This compression or compacting of the air as well as the increasingly larger area of the space between each blade and the preceding blade causes a i'arefaction of the air behind each blade, and the rarefaction will depend upon the distance between the outer ends of the blades as compared with the inner ends thereof. lVhen the distance between the outer ends of the blades exceeds aV certain proportion with re# lation to the distance between theinner ends of the blades, then the rarefaction becomes so great that the air passing outward over the active face of the blade will be caused to eddy or surge over the outer end of the blade into the space back of the blade. The effect of this is that there is produced a chattering or throbbing action when the fan is in .through this clearance space because operation which is intensified as the diameter of the fan is increased until in large fans it may even become destructive to the fan structure.

4 In accordance with the present-invention the fan rotor is provided with a. number of blades,' which may be termed main fan blades, and this nu.nber depends upon the size of the rotor. lllhen the diameter of the fan is such that thespace between 'the peripheral ends of the fan blades exceeds a certain approximate relation to the dista-nce 'betweenthe'intake ends, then there is introduced between the blades other shorter blades with their outer ends atthe periphery of the rotor and terminating at a greater distance from theaxis of the rotor than do the main blades. By this means thel outgoing streams of air from the intake end of the fan instead of compacting against the active faces lof the main blades to such au extent as to cause the chattering -or throbbing referred to are divided up before reachingthe outer edge of the fan into a greater number of streams with 'the sizes of thespaces between the outer ends ofthe fan blades so related to the distances between the inner ends of the fan blades that the rarefaction of the air streams adjacent to the inactive faces of the blades is so reduced as to obliterate the throbbing or chattering and to also prevent any material retardation to the outtiow'of the air in its act/:ive direction.- In the still larger types of fans the spaces between the outer ends of Vthe main blades and of the intermediate blades willagain be too great and the throbbing or chattering will again be present. Under these conditions there is introduced between each intermediate blade and the v next adjacent-main blade an auxiliary blade shorter than the intermediate blade. All the blades, however, terminate at the periphery of the' rotor.

When the fans are in operation there is a clearance space between the sides of the rotor member andthe casing within which the fan is mounted, and because of the resistances offered 'to the outward movement of the air delivered by the fan, a comparatively large volume of air will find Way 1 constitutes a path'of least resistance. Unless provision be made for the prevention of the effect of this returning stream of airit Will retard the inflow of air at the intake of the fan and thus very materially'reduce the efficiency of the fan. i

Inaccordance with the present invention the blowing out ofthe air through the clearance .spaceand the consequent 'lowering' of the eiliciercy of the fan is prevented by carrying the long or main blades for a'distance into the space at the center' of the; wheel though not for a suiicient distance to inter- .'fere with the intake action of the fan.": Under these circumstances any `air .which may findits way backward along the clearance space is met by the in-rushing stream -of air and is carried againto the fan blades to be thrown. outward-toward the delivery Vend of the fan, and this Occurs without retarding to any appreciable extent, the inow of alr at the centralpor'tionof the fah. Furthermore, thecheekplates of the fan rotor terminateat'their inner edges .at a greater distance from the axis ofthe fan than the distance. of the-walls of the casing defining the rotor. The clearance between the cheek plates and the adjacent walls ofthe casing the axis of the rotor than does the definingthe intake opening, while the long or main blades of Athe fan rotor extend toward the center or axis of thefan for a distance closer to said axis than. isV the defining edge Aof .the intake opening in the casing. The initermediateblades' terminate vat the `inner edge of the cheek plates,v and for the'best results Iit is found that the inner'edges of the cheek plates and the inner ends of the -intermediate blades should vterminate. at a point as 'far outward from the dening wall of thev casing orifice as the main blades project inward therefrom toward the' axis of -thus terminates'at a greater distance from wall of the intake opening in 4the casing.

(Consequently, any air which mayd its way `through these clearance. spaces toward Athe intake openingv will indjits way into theactive portion -of the fan beforeilthe ini t l.

each spaced from a correspondin side of the take opening is reached and, therefore, Vin- -stead of retarding'the movement ofthe air eso-. t

revents anyair from eddying or Sligro-mg lliackof the Vactive surfaces of the ljltjtdes1 into the intake opening 'it will participate in the movemento'f the air toward the .active portion of the fan.

The main fan 'blades as well asthe inter# mediate and auxiliary blades are formed with their inner ends tan ential to a `circle -of less diameter thanthe lntakeopening of small circle concentric with the axisdf. the rotor. VThis will Vgive a slightly fonw-ardf throw 'to theoutgoingstreams of ain` and around the peripheral .edgesthereof..

The invention willbe best understood description taken in connection Withgthe ac' speci cation., in which drawings,-

Fig re l 1s a side elevation, with'parts in .section andparts broken away, vof .the rotary with the present invention. Fig. -2 is a sii'nilar. View ofa fan rotor of smaller size than that shown-in Fig. 1. Fig..3 is a section onthe Aline A-B of Fig. 2, showing the fan ii1" position in thefan casing.-v Fig; 4 'is a crosssectfion of a portion yof a fang" constructed in accordance .with the present `infv'ention. F ig. 5 is a similar section of a form of fan heretofore used.v

Referring to the drawings 'there is shown a shaft-'1 which may be taken as a power shaftvto which -a suitable driving force is `appliedand by means, of which the rotor of Fast on the` the fan is carried and driven. shaft 1 are' a suitable number of radial arms 2, the'number depending upon the size of lthe fan rotor and the strains tobe vresisted by the structure. In the drawings butfour radial arms are shown,`but it is to be under Stood that s ix or eight or more arms may "be employed;` as necessary. These arms carry at their 'outer ends an annular cheek or flange 3, having-its periphery l coincident with the.. outer edge of the fan rotor compiying Adrawings forming' part of this memberfof a blast fan made in accordance and also having an edge 5, to which reference will hereinafter be made.

'In the particular structure shown therc ar-e two .n'nular ch'eeks 3 spaced vapart and supporte by arms 2 secured to suitable -hnbs 6 fast upon the shaftl, and the hubs are spaced apa-rt and-are also connected -together` by a suitable drum 7- formed with two inembers secured together at their meeting faces. Betweenthese meeting 'faces is secured a -web .8 which may be, made up of segmental sections extending to the outer periphery of the rotor. The fan is, therefore, made up of a central web and two annular cheeks .web while between the cheeks t e rotor vof the'fan'isprovided with a suitable number 'f fan blades, Aas will .hereinafter appear.

Secured tothe web 7 and the corresponding cheek plate oneach' side thereof is anannu lar series of equally spaced fan blades 9 being heldin lace by suitable angle irons 10, it being un erstood that in lthe particular instance shown the fan is built of metal, the web and cheek plates being of sheet metal of 6 5 from a consideration ofthe following detail l other portion 1 2 of the fan blades extends 130 tangentially at an angle of about-"20 more or less to a line radial to the shaft 1, which line the portion 1'2 of the ytaniblade it 4end to a ring 13. the inner` ends ot the sev eral fan blades 8 beiner all secuned to suelta ring on each side ot the diaphragm 8.

Letit be supposed that a fan having its rotor provided with blades t) as4 described and showirin Figs." 1 and 2. is being rotated counter clockwise, as viewed in said figures'. Considering but one` set of blades on one side of the diaphraem S. which structure might -be used in smaller types offans, it will be seen that the'air within the rotor is scooped up and directed by the tangential members -lQ ot' the fan blades toward the periphery of the fan rotor. This will at once create a vacuum or partial vacuum Ori'ai'efaction at the inner open portion ofthe fan, and the surrounding atmosphere will rush in to restore the normal pressure thus reduced. The oiitwardljtinovino' columns of air directed by the tangentia portions 12 ot' the blades 9 ultimately reach theradial or approximately radial portions 11 of the blades and are thereby thrown more directlyY outward in a radial line than would occur were tht` blades tangential throughout. their length. y i

Considering only-tile blades tl it will be set-.n.that their outer ends; because of the "angential inclination ot' the bladesl are 'spaced apart for a considerable distance which is unich in excess of the spacing. ot' the inner ends of the blades. and this peripheral spacing is also `inteater than though the blades were` radial. The out\\.ardly {iowin; streams of air scooped iip b v the blades are directed by the latter into portions of the fan ot' constantly' inc 'easing cross sectional area. rl`he torward rotation of the tan blades tends to pack or cond-ense the vair against the .active faces of the fan blades. thereby causing -rarefiiction ot' the air streams at the inactive tace of each next precedingblade. it the t'an rotor be' comparatively small. then the relation of the distance between the outer ends ot' two adjacent' fan blades to the distance between the inner end of one ot' the fait blades and tiie next preceding t'an blade. measured on 'a line perpendicular to the active face ot the said preceding lfan blade will be suchthat 'destructive to the fan structure.

lradial portion 1G.

the outgoing` air stieara.` are of .-sutti'u'ent density. even adjacent se da inactde vali ot' the preceding blade. so that there ne tendency, to any material extent. ot' the air streams on leavingr the blade.` to eddy or surge back around the outer edge It the blade into the space back of the bladexiiih relation to its direction of travel. When. however, the

"fan rotors are of greater diameter and there is a marked ditl'erence inthedensity of the air streams in different parts of the space between the active face of a fan blade and the rear face ot the next preceding blade so that there is forn'ied an area otl raretac.- tion innnedia'tely adjacent to the rear oi' thc preceding blade', then there a tendency ot the air when passing beyond the peripheral edges of the blades to eddy or surge-back into the area of rarefaction. and not only retard the outward movement t the air under the action of the tan blades,

but this surging or eddying of the air eurrents sets up throbbings or chattering. which inthe larger types of fans may cvenbecome Even though such beatings oi" throbbings should not. be sufficiently intense to become destructive still they interfere with the smooth runningfof the fan rotor.. To overcome this ditlieulty there 4is introduced midway between the blades 9, other blades 14e each having a tangential portion 15 and Substantially These intermediate blades extend from the periphery -t of the cheek plates to the edge but do 'not extend into the open throat of the fan body. In this structure. which is shown in Fig. :2,'the vbest results 'are obtained'when the distance between the inner end of the tangential portions 15 'and the next preceding blade' 9 'measured on a line .perpeiulicular to the face ot the tangential portion 1iiof said preceding blade as indicated by the dotted liuc b, approximately two-thirds of the distance between the inner end of the tangential portion 12 of the blades 9 and the next precedingblade f) measured on a line. perpendicular to the face of said in'eceding blade as indicated .by the dotted line a. Alsothe. distance from the inner edge of the tangential portion 15 of the blade 14 Aand the face vot' the tangential portion 1Q of the succeedingblade Q measured on a line-perpendicular. to said face as indi 'ated by the dotted line c. should likewise be'less than the distance between the inner edge of a blade` Si and the preceding blade 9 measured on the line a as before. tanccs between the inner edge of any inter.

mediate blade 14. and both the pitx'eding an intermediate blade 14 and the correspond Also the sinn of the disling end of the adjacent blade 9, it being understood that all the blades reach 'to and terminate at the peripheryof the fan rotor, whiclris coincident with the peripheryl of ythe cheek plates.

' Considering a .fan rotor of still. greater diameter, for instance, as indicated in F 1, then the distance between the outer ends of the blades 9 and 14 ultimately becomes so 1 0 great thatthe raret'ied-areas are again producedfand throbbing or beating is set up.

Under these circumstances, it' becomes necessary to introduce between each intermediate blade andthe next succeeding main blade, other auxiliary blades shorterthan the intermediate blades. These blades are ,indicated vat '17 and may be made of a substantial radiahportion 18 and a tangential 4portion 19. The blades 17 reach from -the ,20 periphery of the rotor inward to a point where their inner ends are related to the adj acci-1t blades9- and 14 in thesaine manner as described with relation to t-lie inner ends of the'blades le and the adjacent blades 9.

.25 That is, 'the sum of the distances'betweenthe inner end; of' a blade 17 and the adjacent walls of the blades 9 and 14 should not exceed about oneand one-half times the dis-- tance between the outer`end of a blade 17 30 and thea'dj-acent outer -end of a blade 9. It'

.the fan rotor be still'further enlarged then additional auxiliary 'blades are .added to maintain the approximate equal spacing, as

.. -set' forth.- As 4an example, the'proportions fj5 got.`;1a tan` constructed as described, wherein .both theory and practice have demonstrated the correctness o the proportions, it may be 'stated that -the` Inumber ,of long.- or maifn,

Y blades should be such 'that "the combined .40 Aareas of all the spaces included between the' inner ends of the tangential sections 12 and 'the 'next-i adjacent longer or main blades measure-din a plane perpendicular --to the face of the preceding tangential portion'lQ 4 5 should equalfthe area of the corresponding intake openingin the casing. vIt is found that the total number of blades mayapt proximate one and one-halftinies the-diam'- et'er of the rotor -in feet. -The radial length .of the blades should be about one-eleventh of' the-diameter 'of the rotor. -The tangential u.termediate blades i4 should be about that ofy the rotor of the fan divided by 1.7.

As'wiewed in Fig. 3, the guter c-asingiof- Q 66 the fan is'shown at 2 0 and this 1s also show n/ :5, which though in a measure diagrammatic,

at 21 in Fig. 4, leaving a clearance space 22 between the cheek plates 3 and the adjacent walls of the casing 21.

.It is customary in blastfans as heretofore constructed to carry the blades radially outward from the shaft, as indicated in Fig. 5, where the power shaft is shown at 23 and the blades at 2l. In this casetlie outer casingV 25 -extends down 'toward the intake throat of the fan while the blades carry angle irons :2G designed to support the blades,

but the clearance space is thereby increased.

lV ith a structure such as described in Fig.

still represents. the conditions present in S0l practical forms of blast fans, back `pressure against which the tan works is sufficient to drive a comparatively large quantity of air out through the clearance space and direct it away from the fan. This is due to the fact that the clearance space vpresents but littleA resistance to the escape of the air as conipared with the back pressure on lthe discharge side of the fan. ,Furtlierinord the escaping and wasted stream of air also tends 'toretard the inflow of air at the intake throat ofV tlie'1 fan and so the general )elli cieicy of the fan -is much reduced.

I hare found from both theoretical considerations and from practical experience that the main fan .blades should notextend beyond a certain approximate distance into Vthe intake throat, and further that the cheek plates and the intermediate fan blades should terminate at a greater radial distance Jfrom the axis of the rotor than the defining 'wall or walls of the intake. The best results are obtained when the intake walls are about inidwaybetween the inner ends of the long .blades and the inner ends of the interniediate blades, which inner ends of the intermediate blades 'are coincident with the inner edge of the cheek plates. Now, should air be `forced backward through the clearance space between the cheek plates and the cas ing it is met by the inrushing stream of an entering the throat of the `fan and is directed into contact with the main fan blades to beA again thrown out to the discharge end of t-he' fan. tarding action to any noticeable extent to tlie'inrushing stream of air at the inlet of lthe fan.

What is claimed is:--

41. In a centrifugal blast fan, a fan casing 1.20 with a Vcentral intake opening, a rotor therein having cheekplates with a central open ing larger than the intake opening, and alternate main and :intermediate blades extending inward from the periphery of the 125 rotor approximately.; radial the axis of said rotor for a portion of their vlength and then tangentially for the greater portionof their length, the main blades terminating inside the periphery of the intake opening 130 Thus, no air is lost and there. is no reopeningin'tlre cheekfblades..

2. A blast fan'rotor having nia1n,' intel.` niedlateand auxiliary blades all extending inwardly from' thel periphery of the rotor approximately-radial to the axis thereoflfor i and all having L Substan ia'lly radial outa-1"' the saine .distance and then tangentially for, the lremainder of Atheir length, the mannintenmediate 'and auxiliary blades terminating at respectively greatendi'stances'. from the axis of the rotor.- 3.,.A blast fan-rotor havingflnain, interportions ofthe' same length and' 'the inner portions tangentiahithe'said tangential portions of the diiferent v.sets "of blades'beingA progressively'Shorter in the order named with thetangential portions oi' vthe auxiliary blades shorter than theradial portions of tlie'sarneblades.'

.4g blast-[fan rotor, having cheek plates and ina-1n' andi-intermediate .blades-.extending .inwardly from the periphery andterminat-V ingjrespectiyely inside and .outside .of the `limits of the i-an'oriice, .the intermediate blades terminating atthe inner edge of the cheekplates and the main fan vblades eXtendingbeyond'thesameinto the fan orifice. lA blast .tan having main and interrneL diatejblades extending inwardly from the periphery -and terminating a'trapproximately equal distances inside. and outside of the boundary' of the fan orifice.

- 6. A blast fan having blades extending inwardly from the -periphery and terminating at a distance from the vaXis of'rotatioin thev sum of the areas of the spaces included-be# tween the inner end of each blade -and the surface of the next adjacent blade in a plane perpendicular to the active face of the latter being approximately equal to the area ofthe fan orifice.

7. A blast' fan having main and inter1nediate blades extending inwardly from the periphery and terminatingr at different distances lfrom the axis of rotation, the distance between'the inner vedge of veach main blade and the surface of the' preceding main blade on a line perpendicular to the latter ,being greater than the distance between the inner edge of each intermediate blade and the surface of -the preceding main blade on a line perpendiailar with the latter.

GS gbeing greater than the'disttmce4 between the 8. A blast fan having main and intermeldiate blades. extending inwardly from the periphery andterminating at different distances from the. axis'of rotation, the dis-' tance between the inner edge of each main.

blade and the surface of the preceding main bladeon a line perpendicular tothe latter inner" edge of each intermediate blade and the surface of-'the succeeding main blade on a: line perptnldicular to thel latter.

9. A blast fran haringlinain and- -interni'e'-v .diatelblades extending inwardly-,fromv the periphery 'and-terlninatnlg at diiierent difs'` tances troni the-axisotrotation, the d1s`- A.tance Ybetweenthe .innerfedge of each main blade 'and the-surface of the preceding main blade 'on .a1 .line perpendicular tothelatter being' greater. than the distance between the inner. -edge' of'each intermediate blade and vthesurface ofeitlier the' receding or suc- :ceeding inain blade on a l1ne perpemilicularv rnedlate'and 'auxiliary blades all extendingl vinwardly. from the peri hery of theyrotor to the latter.

' 10.; A.' blast -fan havingacentral intake v'orifice .with blades extending thereinto and free clearance space .opening into the active portion ofthe fan 'at a greater distance from `lhe'airi's'of rotation than the outer limitsof 'the .intake orifice.v '11.'A blast fan having an open and substantially unobstructed intake with fan r blades having substantially radial outer ends extending -to the outer edge of the fan rotor 'and having the linne-r ends entering the intake tangentiallyat an angle of about' 20 to theradius of the fan rotor which the tangential portion of the fan blade would intersect continued -to the periphery of the rotor.. 12. Av blast fan comprising a rotary inemb'er having a central intake and fans having flat portions entering the intake opening to an extent less thanhalf the diameter of said intake opening and provided Witlrsubstantially radial flatcontinuations connected to the tangential portionsof the fan blades and terminating at the outer edge of the rotary member of the fan, the said'tangential por.- tions being at an angle of. about 20 to the radius of the fan rotor which the tangential portions if continued would intersect at the periphery ofv said rotor.

13. A blast fan having cheek plates an inain and intermediate bladeshaving fiat substantially .radial portions extending inwardly from the periphery of the cheek plates .and iiat tangential portions terminating respectively inside and outside of the limits ofthe fan orifice, the intermediate blades terminating at the inner edge ofthe cheek plates and the main fan blades terminating beyond the inner edge of the same and extending into the fan oritice, the said tangential portionsbeing each at an angle of about 20 to the radius of the, fan rotor which the tangential portions would intersect if continued to the periphery of the fan rotor.

14. .Ablast fan comprising a rotary'member having a central substantially open intake throat, main ,blades tangentially disposed for a greater .portion of their length and having their tangential portions entering said throat lor a distance anddisposeo :it an angle et about :2G0 to the radii of the -lan rotor winch the tangential portions would intersect it continued to the periphei?,7 i

of the said rotor, the said main blades terinitiating et their outer ends in substantially radial sections, and shorter blades between the inain blades und also composed of ten'- gential inner and ,substantially radial enter portions, the enter ends of all the blades terinineting et the saine distance from the axis of the rotor.

l5. A blast fan provided With e rotor havf ing a substantially unobstructed central 'in-- take tlnfeat. section and provided with cheek plates beyond the thi-oat section, endian blades mounted between the cheek plates and comprising a seriee et equally spaced blades having their inner ends liet. and at an angle el about 200 each to e radins et thel tain rotor which the inner ,end of the blade if extended would intersect .at the periphery. l of' the sind rotor, the inner end ol each-fan blade entering the throat section for a distance lesswthan halfl the diameter thereof, and other supplemental blades between the' mein blades and having liet tangential p0r-` tioneternnnating at their inner ends et it point exterior to the throat' section, tbede gree ol tangeney ot' the supplemental blades being similar to tha t of the mein blades, and all the blades having their onteiends flat end substantially radial and terminating et the outer periphery et 'the reiger.

itk ble-st ten roter having e' number of `equally spaced main blades and an equal niunbei' ot intermediate blades1 with the sum of the areas of all the spaces between the inner 'ends ot each mein bladel and the active a tace of the preceding blade in a plane perpendicular' thereto, approximately equal to the area of the intakeoritice ot the fan.`

ll". A blast-stan, rotor having a number et niain blades and other Shorter blades all terininatirif et the periphery of the rotor, the totaln'innber .of bladesfbeering such a relation, Substantially as deeeribed,' to the diameter out the rotor' that the peripheral disv tance between the outer endsot the tan of tbe rotor' through'the central openingA thereof exterior ,to the Outer `limit of ich@ lk@ Qpenng of the casing v rny own, l have heretoallixed my signatnn` in the presence of two Witnesses. l

, innerer; F.' Lerner. lfitnesses:

E. W. CANIa C. E. 30me.

,ln testimony that. l cleimthe foregoing asf. 

